Residual carbonates, presence

Sodium a2idodithiocarbonate decomposes with evolution of nitrogen gas on addition of iodine, thus providing a useful quaHtative test for the presence of residual carbon disulfide ia aqueous solutions (25). 

The thermal reactions of CaC204 H20 have been very fully investigated and this substance has been used as a thermal analysis reference material [1058], Dehydration, decomposition to the carbonate, and dissociation to CaO are all well separated, though kinetic characteristics are influenced by the presence of C02, 02 and H20 as well as by the reaction conditions, including heating rate, sample size, and sample container. Kinetic parameters for the oxalate decomposition reaction have been summarized by Gurrieri et al. [1059]. Values of E are close to 314 8 kJ mole-1. Decompositions [1057,1060,1061] of Sr (643—743 K) and Ba (663—743 K) oxalates involves some disproportion of CO, yielding residual carbon. 

It reacts similarly to the disodium salt [1], If heated to 150°C, it decomposes extensively, evolving gas which ignites in air owing to presence of pyrophoric carbon. The residual carbon is also highly reactive [2], The dry powder (lfom solution in liquid ammonia) may ignite if exposed to air as an extended layer, e.g. on filter paper [3],... 

Figure 19 shows the slow coke profiles for the top and bottom zones obtained when 0.0, 0.1, and 0,2% fast coke is present. When no fast coke is present, the catalyst does not bum clean ( 0.2% residue carbon at kiln exit). This is consistent with the rapid rise in bum-off distance at 875 F (469°C) seen in Fig. 17. However, the presence of 0.1% fast coke gives an essentially clean catalyst, using only 0.6 of the bottom zone. Only a quarter of the bottom zone is needed when 0.2% fast coke is present. This improvement in bum-oflf distance is caused by the temperature boost obtained from the rapidly burning fast coke. This temperature boost is shown by the temperature curves in Fig. 20b. The temperature of the catalyst at the top of the upper bed has increased from 875°F (741 K) to 900°F (755 K). This is sufficient to make a large improvement in bum-off distance as shown by Fig. 17.

The XPS results tabulated in Table III clearly illustrate the presence of the formate and its decomposition (95). Prior to adsorption a small amount of residual carbon was present on the surface in carbidic form shown by the C(ls) peak at 282.3 eV binding energy. Allowing for this residual carbon, the XPS-determined coverages clearly show the expected 2 1 0/C ratio. The 0(1 s) peak position observed following heating to 360 K, which was... 

X-ray absorption spectroscopy has proved the presence of rhenium dioxide within this nanostructure [12]. Extraction of the surfactant with various solvents remained inefficient since either the surfactant persists within the composite or the nanostructure is lost. Calcination at mild temperatures as low as 300-350°C in nitrogen atmosphere leads to a mass loss under these pyrolytic conditions of about 50% with only little loss of the nanostructure. Similar results are obtained when the composite is oxidatively treated in an oxygen plasma for not more than ten minutes. Physisorption measurements on the calcined or plasma treated samples show only very small surface areas, which cannot be assigned to a mesoporous structure. Right now we believe that residual carbon may introduce some pore blocking effects within the nanostructure preventing good access of the inner pore surfaces. 

Formation of novel free radical products at an early stage of the Maillard reaction was demonstrated by use of ESR spectrometry. Analyses of the hyperfine structures for various sugar-amino compound systems led to the conclusion that the radical products are N,N -disubstituted pyrazine cation radicals. These new pyrazine derivatives are assumed to be formed by bimolecular condensation of a two-carbon enaminol compound involving the amino reactant residue. The presence of such a two-carbon product in an early stage reaction mixture of sugar with amine was demonstrated by isolation and identification of glyoxal dialkylimine by use of TLC, GLC, NMR, MS and IR. 

These high alkali pressures can be attributed to the presence of unreacted Na2C03 impurity in the original glass samples, even though care was taken to avoid this in the glass preparation. Residual carbonate impurity is a common problem with glass experimentation e.g., see Cable and Chaudhry (50). 

Analysis of the monosaccharide signals in the C-NMR spectrum (103.1, 77.9, 75.0, 71.3 and 66.9) and further assignment of all proton and carbon chemical shifts using H- H COSY and HMQC experiments indicated the presence of a xylose residue. The presence of xylose was confirmed by acid hydrolysis of 44 with aqueous 2N trifluoroacetic acid followed by GC analysis of the corresponding peracetylated alditol. The D-configuration was determined by GC analysis of the l-[(S)-A-acetyl-(2-hydroxypropylamino)]-l-deoxy alditol acetate derivative as for... 

The presence of molten Black Powder combustion products retards the air oxidation of the residual carbon particles. 

The second generation of physical processes occurs in homogeneous phase, but they depend on the processing mode and reaction temperature. At the hot filtration, one can reduce the presence of residual carbon. However, carbon can act as a catalyst, allowing the breaking of the molecules with molecular weights smaller, increasing the selectivity and quality of the final product. It also depends on the filtration mode and the type of cyclone. 

The resulting ash is completely free of organic matter. This is a prerequisite for ensuring accuracy with some analytical techniques (e.g., ICP-MS or electrochemical methods) wherein analyte response may be influenced by the presence of residual carbon or some undigested organic molecules. The resulting solutions are of very acceptable aspect... 

The small amount of PCDD/PCDF detected in 100% paper may be due to the trace amount of chlorine in the paper (from the bleaching process) and from the interaction with the refractory material, which had trace amounts of chlorine. The residual carbon collected in the region of 300-400°C is responsible for the formation of PCDD/PCDF by de nova synthesis. The presence of chlorine and copper in ash, in trace levels, implies the presence of copper chloride, which can play a vital role in the formation of PCDD and PCDF through de nova synthesis [42, 43]. 

The exterior of rice husk ask are composed of dentate rectangular elements, which themselves are composed mostly of silica coated with a thick cuticle and surface hairs. The mid region and inner epidermis contain little silica. Jauberthie et al, confirmed that the presence of amorphous silica is concentrated at the surfaces of the rice husk and not within the husk itself [9]. The properties of rice husk ash and its main composition are presented in Table 8.3. The organic materials consist of cellulose and lignin which turn to CO and CO when rice husk ask burns in air. The ash contains mainly silica (90%), and a small portion of metal oxides ( 5%) and residual carbon obtained from open burning [10]. 

TG analyses confirm the absence of side phases [18,26] and show the presence of only two weight losses the first, at about S03K, is attributable to the elimination of the water molecules firom the interlayers, while the second, at about 673K, is due to the dehydroxylation of the brucite-type layers and to the elimination of the carbonate anions from the interlayers [7], As magnesium content increases, this latter loss is displaced towards the higher temperatures and is only a partial one, on account of the higher affinity of the Mg " " ions for CO2 [32-34]. This phenomenon is also observed for the samples calcined at 923K for 14h the FTIR spectra of these samples confirm the presence of residual carbonates. 

The presence of residual hydroxyl and residual carbon High cost of raw materials... 

We observed similar decarbonization when we pyrolyzed PNMS, ONMS, APNMS, and APNES in the presence of ammonia. The ceramic yields and chemical compositions are shown in Table 4. The pyrolysis of ONMS and PNMS in the presence of ammonia provides an amorphous silicon nitride with a highly reduced level of residual carbon relative to those obtained by pyrolysis in nitrogen. The amount of elemental carbon can be lower than 1 wt%. 

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